Pressure control is widely used in industrial processes or machineries. It affects the quality and productivity of production and is an important factor in triggering reaction in chemical production processes.
An On-line Analyzer paired with a Sample Conditioning System is commonly used for quality control in production lines of petrochemical, food, biotech, and drug industries. The Sample Conditioning System dictates the performance of the On-line Analyzer. It must ensure that the gas flowing into the On-line Analyzer is stable in pressure, temperature and flow.
Usually gas flowing into the On-line Analyzer from the Sample Conditioning System has environmental temperature and pressure. Gas discharged from the On-line Analyzer usually cannot flow back into the production pipeline by itself but rather needs to be pumped back to production or to a recycler. The layout is shown in FIG. 2. Explanations of FIG. 2:
a) 201: Gas source to be pressure-controlled.
b) 202: Sample Conditioning System: a processing system that works with, and is in front of, the On-line Analyzer.
c) 203: On-line Analyzer: an analyzer that takes gas inflow from the Sample Conditioning System and continuously analyzes it.
d) 204: Pump.
e) 101: High Pressure Recovery Tank: for recycling gas.
If the pressure of the recycling tank at the output end of the On-line Analyzer is not stable in pressure, it will cause the gas pressure inside the On-line Analyzer to be unstable. As a result, the reading of the On-line Analyzer will fluctuate abruptly. Therefore, system designers are forced to discharge the analyzed gas into the atmosphere as shown in FIG. 3. Explanation of FIG. 3:
a) 201: same with 201 in FIG. 2.
b) 202: same with 202 in FIG. 2.
c) 203: same with 203 in FIG. 2.
d) 301: Atmosphere.
Another technology in stabilizing gas pressure and recycling gas is shown in FIG. 7. Explanation of FIG. 7:
a) 701 Limit Switch A: a directionless switch for stopping the operation of gas pumping.
b) 702 Tripper Rod: a rigid rod which moves with the wire to a particular position to trigger a Limit Switch.
c) 703 Limit Switch B: a directionless switch for starting the operation of gas pumping.
d) 704 Counterweight: to balance the weight of the Floating Top via the Pulley Set.
e) 705 Pulley: to support the wires and make it easy for the wires to move and change the direction of the force applied.
f) 706 Pulley: same with 705.
g) 707 Floating Top: working together with the Pulley Set and the Counterweight such that when gas flows into the Bucket and raises the Floating Top, the accommodating volume of the Bucket increases without changing the pressure inside the Bucket.
h) 708 Bucket: for accommodating continuous gas inflow.
i) 201 Gas source: source of the gas which needs to be pressure-controlled.
j) 300 Booster Device: capable of drawing in gas from one end, pressurizing the gas, and discharging the gas from the other end.
k) 101: High-Pressure Recovery Tank.
The Bucket has a double-layered shell with high-density silicon oil filled in between the layers so that there is no space between the sides of Floating Top and the shell of the Bucket. The weight of the Floating Top is balanced by counterweights. When gas enters the Bucket, the Floating Top rises and the Tripper Rod declines. When the Tripper Rod touches the Limit Switch B, the Booster Device is started and the gas inside the Bucket is drawn out. Then the Floating Top goes down, causing the Tripper Rod to rise, until the Tripper Rod touches Limit Switch A and the Booster Device stops.
When gas flows into the Bucket, the inertia to raise the Floating Top must be overcome. Also, when the Booster Device is started by the Limit Switch B and ready to pump gas to the High Pressure Recovery Tank, there is the issue of the unstable pressure at the output end causing unstable suction volume. The Floating Top cannot swiftly move to balance the quick changes of gas flow due to its inertia of mass.
This design cannot satisfy the requirement of a stable On-line Analyzer when the pressure fluctuation is large in the recycler, or when the flow volume fluctuation is large at the source. Also, the components are exposed to the atmosphere all the time, the change of characteristics of the material on the surface would make the balance mechanism deteriorate.